1 Definition

Pressure at a point is the average force acting perpendicularly on a unit area surrounding that point. If a force F acts perpendicularly on a surface of area A, the pressure is

P = F / A

• Unit: newton per square metre, N/m², called the pascal (Pa): 1 Pa = 1 N/m².
• Dimensional formula: ML⁻¹T⁻².
• Pressure is a scalar quantity (the force it produces on a surface is always perpendicular to that surface).

Pressure increases when the force increases or when the area decreases.